1. Field of the Invention
The present invention relates generally to polishing pads useful in the manufacture of semiconductor devices or the like. More particularly, the polishing pads of the present invention provide improved planarization from a single pad layer.
2. Discussion of the Related Art
U.S. Pat. No. 5,281,663 describes a polishing pad containing a rigid layer adjacent to a polishing layer. The rigid layer imparts a controlled rigidity to the polishing layer. The resilient layer provides substantially uniform pressure to the rigid layer. During operation, the rigid layer and the resilient layer apply an elastic flexure pressure to the polishing layer to induce controlled flex in the polishing layer to conform to the global topography of the wafer surface while maintaining a controlled rigidity over the local topography of the wafer surface.
U.S. Pat. No. 5,212,910 describes an improved composite polishing pad that includes a first layer of elastic material, a second stiff layer and a third layer optimized for slurry transport. This third layer is the layer against which the wafer makes contact during the polishing process. The second layer is segmented into individual sections physically isolated from one another in the lateral dimension. Each segmented section is resilient across its width yet cushioned by the first layer in the vertical direction. The physical isolation of each section combined with the cushioning of the first layer of material create a sort of "bedspring" effect which enables the pad to conform to longitudinal gradations across the wafer.
Rigid polishing pads are generally used to obtain the degree of planarity necessary. Such rigid pads however, do not conform to surface height variations. Therefore, a need exists for a polishing pad exhibiting the planarization capabilities of a rigid pad and the ability to conform to surface features found in a softer pad.